Slowing of information processing

Neurocognitive problems are one of the most frequent and disabling symptoms associated with ME/CFS. In fact, around 90% of 2073 patients reported having memory/attention deficit problems in a large study in 2001. Crucially, patients often say that physical or mental exertion makes their cognitive problems worse.

A research group from University of Adelaide, South Australia investigating cognitive performance (reaction time, attention, memory, motor functioning, verbal abilities, and visuospatial abilities) in ME/CFS has now published its latest results. In 50 patients, they found that the main cognitive deficit was in ‘reaction time‘ (assessed as reaction times to both simple and complex choices presented on a computer screen) – which was about 50 milliseconds slower on average in patients than in the control group of 50 healthy people. They point out that a basic slowing in information processing speed seems to be at the root of this problem, rather than a deficit in more complex decision making. Interestingly, the slowing of reaction time was not related to psychological status (including depression or anxiety), to the number or severity of ME/CFS symptoms or to everyday functioning.

This very active Australian research group also published (in 2010) an excellent overview (meta-analysis)  of all relevant clinical trials examining cognitive functioning in people with ME/CFS. This review found convincing published evidence of a deficit in reaction time (confirmed in the experiments above); attention (encompassing attention span and working memory); and memory (assessed by verbal and visual memory tests, mostly memory for word lists). Moreover, the deficits in performance of ME/CFS patients were around 0.5–1.0 standard deviations below those of healthy people, a fact which helps to explain the significant impact cognitive problems have on patients’ day-to-day activities and quality of life.